1. Field of the Invention
The present invention relates to an ignition apparatus for an internal combustion engine which supplies a high voltage to a spark plug for each engine cylinder.
2. Description of the Related Art
FIG. 7 is a plan view of an ignition apparatus 1 for an internal combustion engine shown in Japanese Patent Laid-Open No. Hei 7-29751. FIG. 8 is a cross sectional view of the ignition apparatus 1 for an internal combustion engine taken along line VIIIxe2x80x94VIII in FIG. 7. FIG. 9 is a plan view of a wiring module 9 shown in FIG. 9. FIG. 10 is a view of the wiring module 9 when seen from arrow A in FIG. 9. FIG. 11 is an electric circuit diagram of the ignition apparatus 1 for an internal combustion engine shown in FIG. 7.
The ignition apparatus 1 illustrated is used by a simultaneous ignition system for an internal combustion engine, that is, the opposite ends of a secondary coil 6 of each transformer are connected with two spark plugs. The ignition apparatus 1 is provided with three transformers 1A, 1B, 1C, and is used for an internal combustion engine having six cylinders.
The first through third transformers 1A, 1B, 1C of the ignition apparatus 1 are built into a casing 8 that is molded with a resin and has a plurality of high-voltage towers 8a formed at its head. Each of the first through third transformers 1A, 1B, 1C includes a closed magnetic circuit core 2 which forms a hollow-rectangular-shaped closed magnetic circuit, a primary coil 4 which has a conducting wire wound around a primary bobbin 3 surrounding the closed magnetic circuit core 2, and a secondary coil 6 which has a conducting wire wound around a secondary bobbin 5 surrounding the primary coil 4. The first through third transformers 1A, 1B, 1C are fixed to the casing 8 through a resin portion 11 made of a thermosetting resin such as an epoxy resin.
The conducting wire of each primary coil 4 is connected at one end thereof with a corresponding module connector terminal 10a that is one of three first ends of a first wire 10A, and the other or second end of the first wire 10A forms a connector terminal 10b. The connector terminal 10b is electrically connected with an external connector terminal through which it is finally connected with a power supply (not shown) such as the battery of a vehicle. The conducting wire of each primary coil 4 is connected at the other end thereof with a module connector terminal 10c that is one end of a corresponding one of three second wires 10B, and the other end of each second wire 10B forms a connector terminal 10d. The connector terminal 10d of each second wire 10B is electrically connected with an external terminal through which it is finally connected with a corresponding terminal of a switching module (not shown), e.g., a collector of a corresponding one of power transistors which constitute the switching module.
The conducting wire of each secondary coil 6 is connected at its opposite ends with external output terminals 8b of the high-voltage towers 8a, respectively.
The first wire 10A and the second wires 10B are integrally formed with each other through a resin to form the wiring module 9, as shown in FIG. 9.
With the known ignition apparatus for an internal combustion engine as constructed above, the respective transformers 1A, 1B, 1C are arranged in the casing 8 with which the wiring module 9 is integrally formed beforehand, and thereafter the conducting wire of each primary coil 4 is connected at one end thereof with a corresponding module connector terminal 10a of the first wire 10A, and at the other end thereof with the module connector terminal 10c of a corresponding second wire 10B. Also, the conducting wire of each secondary coil 6 is connected at its opposite ends with the corresponding external output terminals 8b of the high-voltage towers 8a. Then, a resin such as an epoxy resin is casted into the casing 8 under a vacuum atmosphere, and solidified or cured in a curing oven at a high temperature to form the resin portion 11. In this manner, the fixing of the respective transformers 1A, 1B, 1C and the insulation of a high voltage can be achieved.
Now, the operation of the known ignition apparatus 1 for an internal combustion engine as constructed above will be explained below.
When coil drivers (not shown) such as power transistors are driven by a control signal from a control unit (not shown) of the internal combustion engine, a primary current flowing through the primary coils 4 is controlled to be supplied and interrupted in an appropriate manner by the coil drivers.
That is, the coil drivers are turned off at prescribed ignition timing of the internal combustion engine thereby to cut off the primary current of the corresponding primary coils 4, whereupon counterelectromotive forces are generated in the primary coils 4 whereby high voltages are produced in the secondary coils 6 of the transformers 1A, 1B, 1C. As a result, the high voltages thus produced are impressed on the spark plugs (not shown) connected with the secondary coils 6, whereby air fuel mixtures in the unillustrated engine cylinders are dielectrically broken down, and fired by sparking of the corresponding spark plugs caused by discharging of secondary current flowing through the respective secondary coils.
With the known ignition apparatus 1 for an internal combustion engine as described above, when the respective transformers 1A, 1B, 1C are arranged in the casing 8, the relative positions among the module connector terminals 10a of the first wire 10A, the module connector terminals 10c of the second wires 10B of the wiring module 9 integrally formed with the casing 8 and the respective ends of the conducting wires of the primary coils 4 have not been fixed, and hence the positional adjustment of the module connector terminals 10a and the one ends of the conducting wires of the respective primary coils 4 as well as the positional adjustment of the module connector terminals 10c and the other ends of the conducting wires of the respective primary coils 4 are individually performed and then welded to each other through welding operation. Therefore, there arises the following problem. That is, the positional adjustment of each primary coil 4 and the wiring module 9 takes time, and in particular, the increased number of transformers 1A, 1B, 1C results in an accordingly increased time for connecting operation.
The present invention is intended to obviate the above-mentioned problem, and has for its object to provide an ignition apparatus for an internal combustion engine in which the positional adjustment of primary coil connector terminals and module connector terminals can be performed with ease, thus making it possible to smoothly carry out the operation of electrically connecting primary coils and a wiring module with each other.
Bearing the above object in mind, the present invention resides in an ignition apparatus for an internal combustion engine including: a casing; a closed magnetic circuit core incorporated in the casing and having sides; a primary coil arranged to surround a part of the sides of the closed magnetic circuit core and having primary coil connector terminals at its opposite ends; and a secondary coil arranged to surround the primary coil and having secondary coil connector terminals at its opposite ends for outputting a high voltage when a current supplied to the primary coil is turned on and off. A wiring module is provided which has module connector terminals connected with the primary coil connector terminals. The wiring module is composed of a plurality of wires integrally formed with each other through a resin for supplying the current to the primary coil. A resin portion is filled in the casing to fixedly attach the closed magnetic circuit core, the primary coil and the secondary coil to an inner surface of the casing. A positioning element, which preferably includes concave portions formed in the primary coil connector terminals and ribs formed on the wiring module and fitted into the concave portions, is arranged between the primary coil and the wiring module for positioning the relative positions of the primary coil connector terminals and the module connector terminals. According to the above arrangement, the positional adjustment of the primary coil connector terminals and the module connector terminals can be easily performed, thus making it possible to carry out the operation of electrically connecting the primary coil and the wiring module with each other in a smooth manner.
The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.